Figure 3.

N₂O formation by the ba₃ oxidase. The rate of N₂O formation, identified by head-space analysis and gas chromatography, is shown at different enzyme concentrations in acetate buffer (pH 4.8) and ascorbate-reduced PMS. The low pH is necessary to suppress nonenzymatic N₂O formation, which increases with pH and may become significant unless specific countermeasures are being taken (25). The graph combines data of duplicate experiments, which were fitted by linear regression at 4.94 (■), 2.47 (⧫), and 1.24 (▵) μM ba₃, respectively; ●, enzyme boiled in 1% SDS for 5 min; □, assay mixture without the enzyme.